1. Field of the Invention
The present invention relates to a headrest for an automotive seat, and particularly to an arrangement for fixing the headrest upon a seat back of the seat via a single headrest stay which extends from the headrest.
2. Description of Prior Art
In the headrests of a type having a single headrest stay to be fixed on a seat back of a seat, a most typical one is cantilever-type headrest having a generally L-shaped stay whose horizontal stay section extends from one lateral side of the headrest and whose vertical stay section extends continuously from that horizontal stay section downwardly to the upper edge of seat back. Thus, the horizontal stay section is fixed to a base frame of headrest, while the vertical stay section is formed with a pair of through-bores which extend transversely therethrough. Such vertical stay section is firmly fastened to a securing bracket fixed on a right-side or left side corner portion in the upper frame section of seat back frame. In this respect, referring to FIG. 2, which shows an embodiment of the present invention though, one could also see an example of conventional headrest arrangement upon a seat back frame. Using this figure, a brief explanation will be made thereof for better understanding.
Namely, the cantilever-type stay (14) comprises a horizontal stay section (14b) and a vertical stay section (14a). As stated above, the horizontal stay section (14b) is fixed to a headrest base frame (24), and one end portion of that section extend from the lateral wall of headrest (14) to continue with the vertical stay section (14a). The lower end portion of vertical stay section (14a) is fixedly fastened by the securing bracket (18). Let us refer in this respect to FIG. 1, an ordinary conventional securing bracket, like the one (18), is formed to have a channel cross-section, comprising a pair of side sections (like 18a, 18b) each having a pair of holes (like 26, 27) formed therein. Correspondingly to those holes, the lower end portion vertical stay section (14a) is formed with a pair of through-bores (like 14a-1, 14a-2).
With the above basic conventional structure, the stay (14) is fixed upon the upper frame section of seat back frame (16) by way of passing a pair of securing bolts (like 20, 20 in FIG. 1) through both foregoing holes of bracket and through-bores of lower portion of headrest stay vertical section (14a) and fastening them all together.
According to this conventional headrest arrangement on seat back, the lower portion of headrest stay vertical section (14a) is strongly pressed together with the securing bracket by means of the bolts in order to enhance the connecting effect of the stay (14) to the seat back frame (16), thereby avoiding a rattling or wobbling between the stay and bracket.
However, such strong fastening force given from the bolts to both stay lower portion and side sections of bracket results in collapse of the stay lower portion as well as in deformation of both sides of bracket. This is because, in general, the diameter-wise rigidity of the stay at that lower portion is not so great and both side sections of bracket are formed by two relatively thin plate materials respectively, thus being vulnerable to a force applied transversely thereof. Consequently, in that case, the same rattling or wobbling problem will arise again between the stay and bracket, and further there will be a great likelihood that the foregoing holes formed in the bracket may be widened undesirably and the bolts may be cut due to the tendency of the horizontal stay section (14b) to be rotated backwardly about the axis of vertical stay section (14a) by a great backward load given from the head of an occupant to the headrest (12) in a collision case.
To eliminate those drawbacks, a solution may be thought to make greater the thickness of both bracket and stay as well as the diameter of bolts, but another problem will arise, such as a dimensional and weight increase in the headrest construction.